Contrary to the definition surroudning, the word "crunker" is a comparative. Used in the phrase, "He's a totally crunker," crunker is a comparitive meant to indicate that he is in fact a more-alchoholic person than someone else. A noun needs to be placed after the word crunker to create a comparison, especially with totally modifying the comparitive.

Alternatively, if totally is replaced with total, it is a superlative, and is completely acceptable.